Location

Calshot Harbour, Tristan da Cunha

Client

IMC Worldwide

Project Status

Completed in 2001

Innovative Engineering in a Remote Location

Tristan da Cunha – known as the most remote permanently inhabited island in the world – suffered major damage when it was hit by an extratropical cyclone. The island was without power for six days, and the breakwater in Calshot Harbour was in urgent need of repairs.

The repair project presented a number of logistical challenges because the island has no airport and can only be reached by boat. All of the supplies and equipment therefore had to be shipped from South Africa – a trip that takes at least seven days by sea.

It proved impossible to transport the 10-tonne concrete breakwater armour units (required for the repair works) to the island in one piece, and an innovative solution needed to be found. Our Stellenbosch office therefore chose to cast the dolosse in halves, and then stitch-cast them together on the island, prior to placement. This was the first time that this method had ever been attempted and it proved successful.

crawler crane

100 tonnes

gantry crane

20 tonnes

weight of each concrete armour unit

10 tonne

All Equipment Shipped to Island

With minimal equipment on the island, we also had to ship over all the equipment needed to perform the repair. This included a 100-tonne crawler crane, an excavator, a 20-tonne gantry crane, as well as all the materials, tools, and other equipment. It was also necessary to bring pontoons in order to take the heavy loads ashore, because only fishing boats and barges are able to enter the shallow harbour. All equipment were disassembled into loads lighter than 18 tonnes to ensure successful shipment and unloading.

The breakwater plays an important role in protecting the tiny island’s transport artery from winter storms and other ocean squalls. The harbour is essential for the long-term survival of its inhabitants.